AKSA's Lender Preamp with 40Vpp Output

[AKSA]

Thank you very much, X.
You are indefatigable!

HD

 

[lehmanhill]

BV,

Best option is to use balanced transformers, made by Sowter, Jensen, and Lundahl. They are expensive, but the best to use because they give galvanic isolation, guarantee to stop earth loop which make hum.

Hugh

@ BV

To expand on the options, since you are in the US, you may find Cinemag transformers at a better price. Still expensive of course, but good performance. Something like a CMLI-15-15B if you want a 1:1 transformer.

 

[xrk971]

Group Buy status update.

JPS64 -2 sets w/ SMT daughterboards, Paid
*Algar Emi - 1 set, TH, Invoice sent
Redarc12 - 1 set, TH, Paid
CFT - 1 set, TH, Paid
Jacques Antoine - 1 set TH, Paid
Silasmellor - 1 set THT, Paid
Bvtrinh- 1 set TH, Paid
*ggetzoff - 1 set TH, Need PayPal address
tubesguy - 1 set TH, Paid
Aatto - 1 set SMT, Paid
*Mordikai - 1 set TH, Need PayPal address
*Johnny2Bad 1 set TH; 1 set SMT, Invoice sent
*vvs07 - 2 sets TH, Need PayPal address
*Fabian85 - 1 set SMT, Need PayPal address
PCGAB - 1 Set(MB) with SMT boards, Paid
*Harry3 - 1 set MB plus TH, Need PayPal address
*meanman64 - 1 set MB plus THT, need PayPal address
Wayne1 - 1 set TH, Paid
*obh - 1 Set(MB) plus TH, Invoice Re-sent
*PJN - 1 set TH, Need PayPal address
*manniraj - 1 set TH, Invoice sent
Erik777 - 1 set TH, Paid
Zman01 - 1 set SMT, Paid
AKSA - 1 set SMT, Paid
xrk971 - 1 set SMT, Paid

The asterisks above (*) indicates members who need to respond.
Thanks to all the folks who have responded and deposited payment.

 

[spind]

I'd like one of the remaining sets, if you still have any unspoken for. TH or SMD, depending upon what is left.

PM being sent
Steve.

 

[xrk971]

GB Status Update

JPS64 -2 sets w/ SMT daughterboards, Paid
*Algar Emi - 1 set, TH, Invoice sent
Redarc12 - 1 set, TH, Paid
CFT - 1 set, TH, Paid
Jacques Antoine - 1 set TH, Paid
Silasmellor - 1 set THT, Paid
Bvtrinh- 1 set TH, Paid
*ggetzoff - 1 set TH, Need PayPal address
tubesguy - 1 set TH, Paid
Aatto - 1 set SMT, Paid
*Mordikai - 1 set TH, Need PayPal address
*Johnny2Bad 1 set TH; 1 set SMT, Invoice sent
*vvs07 - 2 sets TH, Need PayPal address
*Fabian85 - 1 set SMT, Need PayPal address
PCGAB - 1 Set(MB) with SMT boards, Paid
*Harry3 - 1 set MB plus TH, Need PayPal address
*meanman64 - 1 set MB plus THT, need PayPal address
Wayne1 - 1 set TH, Paid
obh - 1 Set(MB) plus TH, Paid
PJN - 1 set TH, Paid
manniraj - 1 set TH, Paid
Erik777 - 1 set TH, Paid
Zman01 - 1 set SMT, Paid
AKSA - 1 set SMT, Paid
xrk971 - 1 set SMT, Paid
spind - 1 set TH, Paid

* indicates response needed. Thank you.

Update on the use of this preamp as a headphone amp: more listening confirms it is a superb headphone amp. Very clean low distortion sound, dynamic and engaging. Absolutely quiet silent when no signal present. No hum or hiss of any sort. The Toshiba 2SA1837 is a superb output transistor. I believe much of the sound quality is attributable to this finest of Toshiba’s audio BJT ever made. The TH version of the daughter board can readily accept the 2SA1837 vs the KSA1381 and with modification of two other resistors, you have a superb headphone amp. An extra TH set of daughterboards may be just the thing here.

 

[maty tinman]

...adding a RK ALPS potentiometer in parallel to TKD one (cheaper solution).

I am sorry but I do not understand what do you mean. Two potentiometers -and different- in parallel?

 

[JPS64]

@maty tinman

TKD (40€) or RK (4€) potentiometer and you choose what you want equipped.

JP

 

[meanman1964]

X , please remove my name . Have to redraw from this groupsbuy . Hopefully I can buy some boards in a later time .

 

[maty tinman]

TKD (40€) or RK (4€) potentiometer and you choose what you want equipped.

Thank you for the answer.

 

[xrk971]

@maty tinman

TKD (40€) or RK (4€) potentiometer and you choose what you want equipped.

JP

Unfortunately the fab house never got back to me so I assume the production went forward. Is there a lower cost pot with same footprint/pin out? Or I suppose we can always go flying leads.

 

[JPS64]

Hi X,

or drill carefully 3 holes for signal in existing pads (signal and soldering on bottom side) and the 2 mechanical grounded pads (soldering on top side). I´ve done this operation on breadboard.

I could supply the template.

JP

 

[xrk971]

Ok, I can handle drilling. A Dremel too drill pretty handy for stuff like this. So the copper tracks are already there and only need holes to make it work?

 

[manniraj]

@XRK where did you get the blue PCB of the voltage doubler board? All I could see on eBay or Aliexpress are the red ones.

 

[xrk971]

I have been buying the blue ones but they seem to only put out 45v. I just ordered these which can do a true 50v (reportedly). They are a bit more compact too. Will have to see what noise performance is once I get it.

Here are the blue ones:
DC/DC Boost Converters 8-32V 12V Step-up to 24v 9-46V 150W 8A 36V Driver Parts | eBay

Here are the newer metal PCB ones that go to 50v:
DC DC boost converter Constant Current Mobile Power supply 250W 10A LED Driver | eBay

250W CV/CC Car Notebook Power Supply LED Boost Driver Step-Up Module DC 8.5V-48V | eBay

 

[bvtrinh]

Thank you!

@ BV

To expand on the options, since you are in the US, you may find Cinemag transformers at a better price. Still expensive of course, but good performance. Something like a CMLI-15-15B if you want a 1:1 transformer.

Thank you! I am currently using those cinemags with my DAC and they work well. At roughly 70 dollars a piece along with the output transformers, it will probably cost more than twice the cost for the boards and parts. However, that is the nature of this hobby.

 

[ggetzoff]

I wonder if Salas has designed something that would power this thing like the SSLV? It can be populated for 45v.

 

[xrk971]

Thank you! I am currently using those cinemags with my DAC and they work well. At roughly 70 dollars a piece along with the output transformers, it will probably cost more than twice the cost for the boards and parts. However, that is the nature of this hobby.

Certainly you could build two sets of this preamp to handle balanced drive for less than the cost of a pair of Cinemags.

 

[xrk971]

Hi X,

or drill carefully 3 holes for signal in existing pads (signal and soldering on bottom side) and the 2 mechanical grounded pads (soldering on top side). I´ve done this operation on breadboard.

I could supply the template.

JP

Hi JP,
They were able to halt the production - please get me the revised Gerbers with RK09 holes and I will redo the order.
Thanks,
X

 

[Harry3]

X
I have sent you an email.

 

[bvtrinh]

Another set please

Certainly you could build two sets of this preamp to handle balanced drive for less than the cost of a pair of Cinemags.

Okay, if there is an extra set available, I would like to purchase it. Thank you!